Display with aging correction circuit

ABSTRACT

A display includes an electroluminescent display panel containing a light emitting material; a video interface circuit for producing an analog video signal for driving the display; an age circuit for supplying a signal representing the age of the light emitting material; an aging correction circuit responsive to the age signal for forming an analog aging correction signal, the aging correction circuit including, controller means responsive to the age signal for producing a digital correction value, and a digital to analog converter for converting the digital correction value to an analog correction signal; and a summing amplifier for summing the analog aging correction signal with the video signal.

FIELD OF THE INVENTION

This invention relates generally to color flat panel displays and, moreparticularly, to an electroluminescent flat panel display with agingcorrection.

BACKGROUND OF THE INVENTION

Electroluminescent displays are flat panel displays that emit light frompixel locations based on the level of signal applied to each pixellocation. Organic electroluminescent displays employ organic thin filmsdeposited at pixel locations to emit light. The intensity of the emittedlight is proportional to current passing through the organic thin films.The color of the emitted light and the efficiency of the energyconversion from current to light are determined by the composition ofthe organic thin films.

FIG. 1 shows a cross section view of a typical prior art active matrixbottom emitting electroluminescent display such as an organic lightemitting diode (OLED) flat panel display 10 of the type shown in U.S.Pat. No. 5,937,272, issued Aug. 10, 1999 to Tang. The OLED display 10includes a transparent substrate 12 that provides mechanical support forthe display device, a transistor switching matrix layer 14, a lightemission layer 18 containing materials forming organic light emittingdiodes, and a cable 20 for connecting circuitry within the flat paneldisplay to video interface circuit 24, located on printed circuit board26. The transparent substrate 12 is typically glass, but othermaterials, such as plastic, may be used. The transistor switching matrixlayer 14 contains a two-dimensional matrix of thin film transistors(TFTs) 16 that are used to select which pixel in the OLED displayreceives image data at a given time. The thin film transistors 16 aremanufactured using conventional semiconductor manufacturing processes,and therefore extra thin film transistors 16 may be used to formcircuitry for a variety of uses. As taught in U.S. Ser. No. 09/774,221filed Jan. 30, 2001, by Feldman et al., the presence of TFTs within anactive matrix flat panel display allows functions other than display tobe implemented on the same substrate as the display function, producinga system-on-panel. The OLED display is responsive to digital controlsignals and analog video signals generated by video interface circuit24.

It is known to those skilled in the art that organic light emittingmaterials undergo an aging process, where changes in the materials causethe light output of a given material for a constant input currentstimulus to change with age. This causes a given image signal to producea different image as the materials age. However, users of organicelectroluminescent displays expect a given image signal to produce thesame image, regardless of the ages of the organic light emittingmaterials. Alternatively, users may expect a given image signal toproduce a pleasing image, although not necessarily the same image,regardless of the ages of the organic light emitting materials. Forexample, a dimmer image, but with proper color balance, may beacceptable, rather than the same, brighter image.

P. Salam, in his paper “OLED and LED Displays with Autonomous PixelMatching,” published in the SID 2001 Digest, pages 67-69, describes aclosed-loop luminance control system that utilizes light sensors placedaround the periphery of an OLED display for sensing pixel light outputto feed back luminance information to a color correction circuit. A“monitoring mode” is used for the pixel light display when the displayis not in use wherein a single or area of pixels, is addressed one colorchannel at a time, and the emitted light is detected to generate acontrol signal.

The signal from the light sensor undergoes analog-to-digital conversion,and a processor calculates the measured light value and stores it.During normal image display, the display controller utilizes this storedluminance information to correct for non-uniformities in the lightoutputs from the pixels, which may occur due to aging. This method iscomplex because it requires a “pixel luminance map” that must storeinformation regarding each pixel, or each area of pixels, which mayrequire a lot of memory. This can be expensive to implement,particularly for portable devices, which are often price sensitive.Additionally, the “pixel luminance map” memories must be updatedperiodically, and therefore must be either a volatile or a rewritablevolatile memory. Volatile memories typically consume more power thannon-volatile memories, in order to maintain their contents. Non-volatilememories such as FLASH consume less power when not being written, buthave a limited number of update cycles prior to failure. Therefore, a“pixel luminance map” may be costly, power inefficient, and have limitedlife.

U.S. Pat. No. 6,081,073, issued Jun. 27, 2000 to Salam, describes acircuit and method for minimizing luminance and color variation in alight emitting diode matrix display, where light output is measured andstored, and a microprocessor or controller controls the measurement andcorrection process. Again, this method of performing luminance and colorcorrection utilizes a memory map storing information about each displaypixel, and therefore may be unnecessarily complex.

International application WO99/41732, published Aug. 19, 1999, byMatthies et al. describes several methods for correcting brightness dueto OLED materials aging and pixel non-uniformity. These methods includemeasuring a physical aspect regarding light emitting pixels, performingcalculations, and changing the current supplied to these light emittingpixels based on these measurements, in relation to stored accumulatedcurrent-values. This method directly modulates OLED current, and musttherefore operate at the pixel level. However, display systems typicallysupply image information to displays using analog voltages andelectronics within the display, or within the drivers that directlysupply pixel current to pixels, to convert the voltage information intocurrent. It is often desirable to modify these analog voltages, and notthe currents to which the input analog voltages are converted.

There is a need therefore for an improved means of modifying analogvideo signals in a display device for the purpose of compensating forthe aging of the corresponding organic light emitting materials that thesignals drive, utilizing a simplified circuit.

SUMMARY OF THE INVENTION

The need is met according to the present invention by providing adisplay, that includes an electroluminescent display panel containing alight emitting material; a video interface circuit for producing ananalog video signal for driving the display; an age circuit forsupplying a signal representing the age of the light emitting material;an aging correction circuit responsive to the age signal for forming ananalog aging correction signal, the aging correction circuit including,controller means responsive to the age signal for producing a digitalcorrection value, and a digital to analog converter for converting thedigital correction value to an analog correction signal; and a summingamplifier for summing the analog aging correction signal with the videosignal.

Advantages

The display according to the present invention is advantageous in thatit exhibits a near constant luminance and/or color balance for givenanalog video voltages as the light emitting materials of anelectroluminescent display age. The circuit is optimized forcompensating analog video channels, and therefore is simpler, more costefficient, and benefits from higher manufacturing yields than previousmethods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the structure of a prior artorganic electroluminescent display;

FIG. 2 is a schematic diagram showing an aging correction circuit for anorganic electroluminescent display according to the present invention,where analog aging correction signals are combined with analog videosignals;

FIG. 3 is a schematic diagram showing one embodiment of the agingcorrection circuit containing a controller, and one memory, one latch,and one digital-to-analog converter per analog video channel;

FIG. 4 is a schematic diagram showing an alternative embodiment of theaging correction circuit containing a controller, one memory, one latch,and one digital-to-analog converter controlling all analog videochannels;

FIG. 5 is a schematic diagram showing a further alternative embodimentof the aging correction circuit containing a controller connected to onememory, and one latch and digital-to-analog converter per analog videochannel;

FIG. 6 is a schematic diagram showing one implementation of the agingcorrection circuit containing a controller connected to one latch anddigital-to-analog converter per analog video channel;

FIG. 7 is a schematic diagram showing a conventional implementation ofthe aging correction circuit where all components of the agingcorrection circuit are implemented on a printed circuit board;

FIG. 8 is a diagram of an organic electroluminescent display showing itsactive area and an area where additional circuitry may be implemented;

FIG. 9 is a schematic diagram showing an implementation of the presentinvention where amplifiers are implemented within the organicelectroluminescent display, and all other components are implemented ona printed circuit board;

FIG. 10 is a schematic diagram showing an implementation of the presentinvention where latches, digital-to-analog converters, and amplifiersare implemented within the organic electroluminescent display, and allother components are implemented on a printed circuit board;

FIG. 11 is a schematic diagram showing an implementation of the presentinvention where memories, latches, digital-to-analog converters, andamplifiers are implemented within the organic electroluminescentdisplay, and all other components are implemented on a printed circuitboard;

FIG. 12 is a schematic diagram showing an implementation of the presentinvention where a controller, memories, latches, digital-to-analogconverters, and amplifiers are implemented within the organicelectroluminescent display, and all other components are implemented ona printed circuit board; and

FIG. 13 is a schematic diagram showing an implementation of the presentinvention where an age circuit is implemented within the organicelectroluminescent display;

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 2, an electroluminescent display system generallydesignated 100 according to the present invention includes anelectroluminescent display panel 102 driven by one or more agingcorrected analog video signals 104. A video interface circuit 24produces analog video signals 108 and control signals 110. An agingcorrection circuit 112 is responsive to an electroluminescent displayage input from an age circuit 118, to produce analog correction signals114. The analog correction signals are combined with the analog videosignals 108 within summing amplifiers 116. The electroluminescentdisplay panel 102 contains light emitting materials. For multicolordisplays, the light emitting materials that emit the different colors oflight may age at different rates.

Typically, an age for each color of light emitting materials isprovided, since the light emitting materials for different colors age atdifferent rates. However, a single overall age signal may be presentedto a multiplicity of video channels when the light emitting materials ofthese video channels age similarly.

The age circuit 118 may supply one average age of the light emittingmaterials, an average age of each light emitting material in amulticolor electroluminescent display, an average age of the lightemitting material for subset areas of the active area, an average age ofeach light emitting material for subset areas of the active area, anaverage age of the light emitting materials for each pixel within theactive area, or the age of each light emitting material at each pixel ofthe active area. The granularity of age measurement depends on atradeoff between design complexity, cost, the profiles of the aging ofthe light emitting materials, and power consumption.

Various means of measuring the age of the OLED may be used. For example,age may be measured by counting the time the OLED has been driven.Alternatively, age may be indirectly measured by using a light detectorto measure the actual light output of the electroluminescent display,and comparing it to the expected light output for the given driveconditions, as described in U.S. Pat. No. 6,081,073, referenced above.This light output may be taken from the display of normal images, orfrom test patterns displayed during inactive periods, as described bySalam, in his paper “OLED and LED Displays with Autonomous PixelMatching,” referenced above. Age may also be indirectly measured byusing a reference pixel. In one method, the light output of a referencepixel formed within the electroluminescent display panel 102 emitslight, and the light output is sensed, as described in copending U.S.patent application Ser. No. 09/707,223, filed Nov. 6, 2000 by Cok etal., and allowed Jul. 3, 2001.

In a second method, the electrical characteristics of a reference pixelare measured. The measured electrical characteristic must changeproportionally to the OLED material's age. This method is described incopending U.S. patent application Ser. No. 09/577,241, filed May 24,2000 by Cok et al. When indirect measurements are used for measuring theage of light emitting materials, the age circuit 118 may produce ameasured value that is related to age, rather than an actualchronological age. The aging correction circuit 112 then converts thismeasured value into a chronological actual age via a functionalrelationship.

A number of implementations exist for the aging correction circuit 112.One embodiment is shown in FIG. 3. Here, the aging correction circuit112 contains a controller 120, one or more memories 122, one or morelatches 124, and one or more digital-to-analog converters 126. Thecontroller 120 may be implemented as custom digital logic, a programmedmicroprocessor, a microcontroller, or digital signal processor, and isresponsive to age input from age circuit 118. The memories 122 hold agecorrection information, where each memory address corresponds to apredetermined age, and the contents of each memory location contain adigital voltage difference based on the predetermined age. Thus, thememories 122 are used as correction value look-up tables. Because thesememories 122 do not contain a “pixel luminance map,” the size of thememories used in the current embodiment are typically much smaller thanthose used to store a pixel luminance map. The memories may be volatileor non-volatile. Volatile memories are useful for use with differentelectroluminescent display panels 102 having different agingcharacteristics, which occurs relatively often. However, volatilememories require initialization prior to use in aging correction.Alternatively, non-volatile memories are useful when the agingcorrection circuit 112 is normally operated with a singleelectroluminescent display, and therefore does not need initializationprior to every use.

Non-volatile memories may be read-only memory (ROM), electricallyprogrammable read-only memory (EPROM), electrically erasableprogrammable read-only memory (EEPROM), or FLASH memory. The latter twotypes of memory are reprogrammable, and therefore allow for updates tothe lookup table for better accuracy in the future, or for re-use of thecircuitry with different devices or organic light emitting materials.However, the frequency of update is relatively low compared to thefrequency of update of a “pixel luminance map,” and therefore the numberof write cycles for a FLASH device will usually not be a concern.

Latches 124 are used to synchronize the digital aging correction valueto the clock controlling the digital-to-analog converters 126. Thelatches 124 may be omitted if this synchronization occurs inherently asa part of circuit operation, or if the memories 122 contain a latchingfunction.

Utilizing the input age, the controller 120 produces a correspondingmemory address for the memories 122. The address is sent to the memories122, and corresponding digital aging correction values are read fromthese memories 122. When present, latches 124 then latch these digitalaging correction values. The digital-to-analog converters 126 thenconvert these digital aging correction values to analog form.

FIG. 4 shows an embodiment of the present invention where the agingcorrection circuit 112 contains only one memory 122, one latch 124, andone digital-to-analog converter 126. The output of the aging correctioncircuit 112 is combined with more than one video channel using summingamplifiers 116. This embodiment is useful where two different lightemitting materials exhibit the same, or relatively close, agingprofiles, or where reduced complexity of the aging correction circuit112 is desired. This embodiment has the advantages of being simple,thereby reducing cost, using fewer materials, and improving circuityields.

FIG. 5 shows an embodiment of the present invention where the agingcorrection circuit 112 contains a single memory 122, a controller 120,one or more latches 124, and one or more digital-to-analog converters126. Controller 120 is responsive to organic electroluminescent displayage input 118 and reads appropriate aging-to-voltage correction datafrom memory 122. When multiple color channels are present, thecontroller 120 computes the appropriate aging-to-voltage correctionvalue for one color channel at a time, and stores this value in theappropriate latch 124. Once a new value is stored in latch 124, thecorresponding digital-to-analog converter 126 converts this digitalvalue to analog.

Controller 120 synchronizes the look-up operation, latching, and thedigital-to-analog conversion. Because the light emitting materials agingprocess is relatively slow (measured in hours) as compared to thelook-up, computation, latching, and digital-to-analog conversion processusing conventional clock periods (measured in hundreds of microseconds),this embodiment may be utilized to reduce the parts count in thecircuit. Therefore, this embodiment reduces materials and cost, andimproves yields over more complex embodiments.

FIG. 6 shows an embodiment of the present invention where the agingcorrection circuit 112 contains controller 120, one or more latches 124,and one or more digital-to-analog converters 126. This embodiment doesnot use a memory look-up table, but instead relies on a mathematicalrelationship to directly calculate an aging-to-voltage correction valuevia computations performed by controller 120. Different mathematicalrelationships may be used for different light emitting materials withinthe organic electroluminescent display 102. The digital age-to-voltagecorrection values are stored in latches 124, and converted to analogvoltages by digital-to-analog converters 126. This embodiment is usefulwhere the mathematical relationship between the age of the lightemitting materials and light output is relatively simple and thereforedoes not require a very powerful controller for computation. Likewise,this embodiment is useful when the aging process of the materials isslow enough so that complex calculations may be performed over arelatively long period of time. This embodiment has the advantage ofeliminating the memories associated with lookup tables, and thereforerequires fewer materials, reduces cost, improves yields, and reducesmanufacturing steps, since manufacturing processes associated withmemories are often different from those associated with digital logic.

FIG. 7 shows the conventional placement of the various elements of theelectroluminescent display system 100. Conventionally, OLED age circuit118, the aging correction circuit 112, the video interface circuit 24,and the summing amplifiers 116 would be components mounted on a circuitboard 30. The aging corrected analog video signals 104 are then suppliedto the organic electroluminescent display panel 102 via a cable 20. Thecable 20 connects to the printed circuit board 26 at connector 28.

As disclosed in U.S. Ser. No. 09/774,221, referenced above, circuitrymay be integrated on the same substrate as an active matrixelectroluminescent display. Therefore, all, or a part of the circuitrydescribed herein with respect to aging correction may be implemented onthe electroluminescent display's substrate. FIG. 8 shows the basicstructure of such an electroluminescent display system 100.Electroluminescent display panel 102 includes an active area 130 inwhich the light emitting materials and pixels of the electroluminescentdisplay panel 102 are located. Additionally, since thin film transistorsare located within the active area 130, it is relatively simple to formadditional circuitry 132 including additional thin film transistorsaround the periphery of the active area 130. For example, this circuitry132 may be placed close to cable 20, if it is responsive to signalscarried over the cable 20, and the output of the circuitry 132 is usedto control circuitry within the active area 130. Alternatively, existingcircuitry within active area 130 may be modified to include all of, orportion of, additional circuitry 132.

FIG. 9 shows an embodiment of the present invention where the summingamplifiers 116 are physically located on the electroluminescent displaypanel 102 within circuitry 132. Preferably, the summing amplifiers 116are placed around the periphery of the active area 130. One or moreanalog correction signals 114, along with analog video signals 108, aretransmitted over cable 20 to the electroluminescent display 102. Thesumming amplifiers 116 easily integrate into the manufacturing processof the electroluminescent display panel 102, since such analog circuitryis already formed within the electroluminescent display itself toaccommodate the analog video channels. This embodiment has the advantageof reducing parts count on the printed circuit board 26, utilizing highdensity integration technology on the electroluminescent display panel102, reducing overall system cost.

FIG. 10 shows a further embodiment of the present invention where thelatches 124, the digital-to-analog converters 126 and the summingamplifiers 116 are physically located on the electroluminescent display102 within circuitry 132. Typically, the latches 124, thedigital-to-analog converters 126, and the summing amplifiers 116 areplaced around the periphery of the active area 130. The digitalaging-to-color voltage correction output by the memories 122 on theprinted circuit board 26, along with analog video signals 108, aretransmitted over cable 20 to the electroluminescent display panel 102. Adigital transmission circuit 136 performs a conversion of the digitalaging-to-color voltage correction value to the transmission format. Adigital receiver circuit 140, located within circuitry added to theelectroluminescent display panel 102, receives these transmittedcorrection values, and stores them in the appropriate latch 124 on theelectroluminescent display panel 102. The digital aging-to-color voltagecorrection values are transmitted digitally over cable 20. This digitaltransmission can utilize serial or parallel transmission format. Serialtransmission is preferred, since fewer conductors are required,minimizing materials and therefore cost. Serial transmission is oftenslower than parallel transmission. However, since the aging rate of thelight emitting materials is very slow in comparison to conventionalserial transmission rates, it is normally acceptable to transmit at thislower rate. This embodiment has the advantage of reducing parts count onthe printed circuit board 26, utilizing high density integrationtechnology on the electroluminescent display panel 102, reducing overallsystem cost.

FIG. 11 shows a further embodiment of the present invention where thememories 122, latches 124, the digital-to-analog converters 126 and thesumming amplifiers 116 are physically located on the electroluminescentdisplay panel 102 within circuitry 132. Typically, the memories 122, thelatches 124, the digital-to-analog converters 126 and the summingamplifiers 116 are placed around the periphery of the active area 130.Controller 120 on the printed circuit board 26 computes the digitalmemory address values. These digital memory address values, along withanalog video signals 108, are transmitted over cable 20 to theelectroluminescent display panel 102. A digital transmission circuit 136performs a conversion of the digital memory address values to thetransmission format. A digital receiver circuit 140, located withincircuitry added to the electroluminescent display panel 102, receivesthese transmitted correction values, and routes them to the appropriatememories 122 on the electroluminescent display panel 102. Thisembodiment has the advantage of further reducing parts count on theprinted circuit board 26, utilizing high density integration technologyon the electroluminescent display panel 102, reducing overall systemcost.

FIG. 12 shows a further embodiment of the present invention where theentire aging correction circuit 112, the electroluminescent display ageinput 118, and the summing amplifiers 116 are physically located on theelectroluminescent display panel 102 within circuitry 132. Typically,aging correction circuit 112, the organic electroluminescent display ageinput 118, and the summing amplifiers 116 are placed around theperiphery of the active area 130. The video interface circuit 24 remainson the printed circuit board 26. This embodiment places the entire agingcorrection functionality on the electroluminescent display panel 102itself, making the aging correction operation and manufacturingindependent of the system designer.

Additionally, the integration of the aging correction circuit 112, theelectroluminescent display age input 118, and the summing amplifiers 116on the electroluminescent display panel 102 requires fewer components tobe placed on the printed circuit board 26, reducing circuit boardmaterials and cost. Since no additional signals must be transmitted overconnector 28 and cable 20, the same pinout may be used for anelectroluminescent display with and without aging correction. Thisincreases the flexibility of the electroluminescent display system 100,and allows electroluminescent displays with and without aging correctionto be used in the electroluminescent display system interchangeably.

FIG. 13 shows a further embodiment of the present invention wherecircuitry 132 on the electroluminescent display panel 102 includes theage circuit 118. The age of the light emitting materials of theelectroluminescent display panel 102 is supplied to the age correctioncircuit 112 located on printed circuit board 26 via one or moreconductors in cable 20. The placement of the age circuit 118 on theelectroluminescent display panel 102 allows the measurement of materialsage to be coupled to the electroluminescent display panel 102, and notphysically a part of circuitry external to the electroluminescentdisplay panel 102. Thus, a different electroluminescent display panel102 can be plugged in to connector 28, and the age correction circuit112 would operate correctly for this new display, within the need forreprogramming. This increases the usability of the electroluminescentdisplay system 100, decreasing integration costs, and allowing complexaging correction circuitry 112 to be implemented off of the displaysubstrate and in integrated circuitry, where manufacturing yields arecurrently higher.

The above embodiments described in relation to the integration onto theOLED substrate are in relation to the embodiment of FIG. 3. Similarembodiments in relation to FIGS. 4-6, can be readily implemented by aperson of ordinary skill in the art, since the basic methods andreasoning are similar.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention. For example, these aging correction techniques may beused for both passive and active matrix organic electroluminescentdisplays, although the integration of transistor circuitry on passivematrix displays is not likely. Additionally, organic electroluminescentdisplays with color changing materials or color filters typically use asingle color light emitting material. The embodiments described hereinmay be used for such devices, and therefore fall within the scope of thepresent invention. Although the embodiments herein were described inrelation to signal transmission between a printed circuit board and anelectroluminescent display via a cable, other interface means, such asoptical and electromagnetic transmission of signals, fall within thescope of the present invention of an aging correction means by alteringanalog video signals.

PARTS LIST

10 organic light emitting diode flat panel display

12 transparent substrate

14 transistor switch matrix layer

16 thin film transistor

18 light emission layer

20 cable

24 video interface circuit

26 printed circuit board

28 connector

100 electroluminescent display system

102 electroluminescent display panel

104 aging corrected analog video signal

108 analog video signal

110 control signals

112 aging correction circuit

114 analog correction signal

116 summing amplifier

118 age circuit

120 controller

122 memory

124 latch

124 digital-to-analog converter

126 active area

130 circuitry

132 digital transmission circuit

136 digital receiver circuit

What is claimed is:
 1. A display, comprising: a) an electroluminescentdisplay panel containing a light emitting material; b) a video interfacecircuit for producing an analog video signal for driving the display; c)an age circuit for supplying a signal representing the age of the lightemitting material; d) an aging correction circuit responsive to the agesignal for forming an analog aging correction signal, the agingcorrection circuit including controller means responsive to the agesignal for producing a digital correction value, and a digital to analogconverter for converting the digital correction value to an analogcorrection signal; and e) a summing amplifier for summing the analogaging correction signal with the video signal.
 2. The display claimed inclaim 1, wherein the electroluminescent display is an organic lightemitting diode display.
 3. The display claimed in claim 1, wherein theage circuit includes a clock for measuring the amount of time theelectroluminescent display has been driven.
 4. The display claimed inclaim 1, wherein the age circuit includes means for measuring a testpattern displayed on the electroluminescent display.
 5. The displayclaimed in claim 1, wherein the age circuit includes means for measuringone or more electrical properties of a reference pixel located withinthe electroluminescent display.
 6. The display claimed in claim 1,wherein the age circuit includes means for measuring the light output ofa reference pixel located within the electroluminescent display.
 7. Thedisplay claimed in claim 1, wherein the age circuit supplies one averageage of the light emitting materials.
 8. The display claimed in claim 1,wherein the age circuit supplies an average age of each light emittingmaterial in a multicolor electroluminescent display.
 9. The displayclaimed in claim 1, wherein the age circuit supplies an average age ofthe light emitting materials for subset areas of the electroluminescentdisplay.
 10. The display claimed in claim 1, wherein the age circuitsupplies an average age of each light emitting material for subset areasof the electroluminescent display.
 11. The display claimed in claim 1,wherein the age circuit supplies an average age of the light emittingmaterials for each pixel within the electroluminescent display.
 12. Thedisplay claimed in claim 1, wherein the age circuit supplies the age ofeach light emitting material at each pixel of the electroluminescentdisplay.
 13. The display claimed in claim 1, wherein the controllermeans includes a controller, a memory for storing age-to-voltagecorrection values addressable by the controller, and a latch for holdingthe age-to-voltage correction values output by the memory.
 14. Thedisplay claimed in claim 13, wherein the memory is volatile.
 15. Thedisplay claimed in claim 13, wherein the memory is nonvolatile.
 16. Thedisplay claimed in claim 15, wherein the non-volatile memory is aread-only memory (ROM).
 17. The display claimed in claim 15, wherein thenon-volatile memory is a FLASH memory device.
 18. The display claimed inclaim 15, wherein the non-volatile memory is an electricallyprogrammable read-only memory (EPROM).
 19. The display claimed in claim15, wherein the non-volatile memory is an electrically erasableprogrammable read-only memory (EEPROM).
 20. The display claimed in claim13, wherein the memory and the controller are formed on a commonsubstrate.
 21. The display claimed in claim 13, wherein the latches arelocated within the memories.
 22. The display claimed in claim 1, whereinone or more of the circuits selected from the group comprising the agecircuit, the aging correction circuit and the summing amplifier iscircuitry physically located on a common substrate with theelectroluminescent display panel.
 23. The display claimed in claim 22,wherein the circuitry located within the electroluminescent displayincludes the age circuit.
 24. The display claimed in claim 23, whereinthe age circuit supplies one average age of the light emittingmaterials.
 25. The display claimed in claim 23, wherein the age circuitsupplies an average age of each light emitting material in a multicolorelectroluminescent display.
 26. The display claimed in claim 23, whereinthe age circuit supplies an average age of the light emitting materialsfor subset areas of the electroluminescent display.
 27. The displayclaimed in claim 23, wherein the age circuit supplies an average age ofeach light emitting material for subset areas of the electroluminescentdisplay.
 28. The display claimed in claim 23, wherein the age circuitsupplies an average age of the light emitting materials for each pixelwithin the electroluminescent display.
 29. The display claimed in claim23, wherein the age circuit supplies the age of each light emittingmaterial at each pixel of the electroluminescent display.
 30. Thedisplay claimed in claim 22, wherein the circuitry located within theelectroluminescent display includes the summing amplifiers.
 31. Thedisplay claimed in claim 1, wherein the controller means includes acontroller responsive to the output of the age circuit for calculatingage-to-voltage correction values, and a latch for holding theage-to-voltage correction values output by the memory.
 32. The displayclaimed in claim 22, wherein the aging correction circuit includes adigital-to-analog converter and a digital receiver circuit for receivingdigital age-to-voltage correction values, located within circuitry on acommon substrate with the electroluminescent display panel.
 33. Thedisplay claimed in claim 32, wherein the aging correction circuitadditionally includes a latch, located within circuitry on a commonsubstrate with the electroluminescent display panel.
 34. The displayclaimed in claim 33, wherein the aging correction circuit locatedadditionally includes a memory, located within circuitry on a commonsubstrate with the electroluminescent display panel.
 35. The displayclaimed in claim 34, wherein the aging correction circuit locatedadditionally includes a controller, located within circuitry on a commonsubstrate with the electroluminescent display panel.
 36. The displayclaimed in claim, 32, wherein the digital receiver circuit is a parallelreceiver.
 37. The display claimed in claim 32, wherein the digitalreceiver circuit is a serial receiver.
 38. The display claimed in claim32, wherein the digital receiver circuit contains a demultiplexingcircuit, so that a received digital age-to-voltage correction value maybe routed to one of a multiplicity of video channels.